/***************************************************************************

    schedule.c

    Core device execution and scheduling engine.

****************************************************************************

    Copyright Aaron Giles
    All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are
    met:

        * Redistributions of source code must retain the above copyright
          notice, this list of conditions and the following disclaimer.
        * Redistributions in binary form must reproduce the above copyright
          notice, this list of conditions and the following disclaimer in
          the documentation and/or other materials provided with the
          distribution.
        * Neither the name 'MAME' nor the names of its contributors may be
          used to endorse or promote products derived from this software
          without specific prior written permission.

    THIS SOFTWARE IS PROVIDED BY AARON GILES ''AS IS'' AND ANY EXPRESS OR
    IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
    WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    DISCLAIMED. IN NO EVENT SHALL AARON GILES BE LIABLE FOR ANY DIRECT,
    INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
    (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
    SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
    HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
    STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
    IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
    POSSIBILITY OF SUCH DAMAGE.

***************************************************************************/

#include "emu.h"
#include "profiler.h"
#include "debugger.h"


//**************************************************************************
//  DEBUGGING
//**************************************************************************

#define VERBOSE 0

#define LOG(x)	do { if (VERBOSE) logerror x; } while (0)



//**************************************************************************
//  CONSTANTS
//**************************************************************************

// internal trigger IDs
enum
{
	TRIGGER_INT 		= -2000,
	TRIGGER_YIELDTIME	= -3000,
	TRIGGER_SUSPENDTIME = -4000
};



//**************************************************************************
//  EMU TIMER
//**************************************************************************

//-------------------------------------------------
//  emu_timer - constructor
//-------------------------------------------------

emu_timer::emu_timer()
	: m_machine(NULL),
	  m_next(NULL),
	  m_prev(NULL),
	  m_param(0),
	  m_ptr(NULL),
	  m_enabled(false),
	  m_temporary(false),
	  m_period(attotime::zero),
	  m_start(attotime::zero),
	  m_expire(attotime::never),
	  m_device(NULL),
	  m_id(0)
{
}


//-------------------------------------------------
//  ~emu_timer - destructor
//-------------------------------------------------

emu_timer::~emu_timer()
{
}


//-------------------------------------------------
//  init - completely initialize the state when
//  re-allocated as a non-device timer
//-------------------------------------------------

emu_timer &emu_timer::init(running_machine &machine, timer_expired_delegate callback, void *ptr, bool temporary)
{
	// ensure the entire timer state is clean
	m_machine = &machine;
	m_next = NULL;
	m_prev = NULL;
	m_callback = callback;
	m_param = 0;
	m_ptr = ptr;
	m_enabled = false;
	m_temporary = temporary;
	m_period = attotime::never;
	m_start = machine.time();
	m_expire = attotime::never;
	m_device = NULL;
	m_id = 0;

	// if we're not temporary, register ourselves with the save state system
	if (!m_temporary)
		register_save();

	// insert into the list
	machine.scheduler().timer_list_insert(*this);
	return *this;
}


//-------------------------------------------------
//  init - completely initialize the state when
//  re-allocated as a device timer
//-------------------------------------------------

emu_timer &emu_timer::init(device_t &device, device_timer_id id, void *ptr, bool temporary)
{
	// ensure the entire timer state is clean
	m_machine = &device.machine();
	m_next = NULL;
	m_prev = NULL;
	m_callback = timer_expired_delegate();
	m_param = 0;
	m_ptr = ptr;
	m_enabled = false;
	m_temporary = temporary;
	m_period = attotime::never;
	m_start = machine().time();
	m_expire = attotime::never;
	m_device = &device;
	m_id = id;

	// if we're not temporary, register ourselves with the save state system
	if (!m_temporary)
		register_save();

	// insert into the list
	machine().scheduler().timer_list_insert(*this);
	return *this;
}


//-------------------------------------------------
//  release - release us from the global list
//  management when deallocating
//-------------------------------------------------

emu_timer &emu_timer::release()
{
	// unhook us from the global list
	machine().scheduler().timer_list_remove(*this);
	return *this;
}


//-------------------------------------------------
//  enable - enable/disable a timer
//-------------------------------------------------

bool emu_timer::enable(bool enable)
{
	// reschedule only if the state has changed
	bool old = m_enabled;
	if (old != enable)
	{
		// set the enable flag
		m_enabled = enable;

		// remove the timer and insert back into the list
		machine().scheduler().timer_list_remove(*this);
		machine().scheduler().timer_list_insert(*this);
	}
	return old;
}


//-------------------------------------------------
//  adjust - adjust the time when this timer will
//  fire and specify a period for subsequent
//  firings
//-------------------------------------------------

void emu_timer::adjust(attotime start_delay, INT32 param, attotime period)
{
	// if this is the callback timer, mark it modified
	device_scheduler &scheduler = machine().scheduler();
	if (scheduler.m_callback_timer == this)
		scheduler.m_callback_timer_modified = true;

	// compute the time of the next firing and insert into the list
	m_param = param;
	m_enabled = true;

	// clamp negative times to 0
	if (start_delay.seconds < 0)
		start_delay = attotime::zero;

	// set the start and expire times
	m_start = scheduler.time();
	m_expire = m_start + start_delay;
	m_period = period;

	// remove and re-insert the timer in its new order
	scheduler.timer_list_remove(*this);
	scheduler.timer_list_insert(*this);

	// if this was inserted as the head, abort the current timeslice and resync
	if (this == scheduler.first_timer())
		scheduler.abort_timeslice();
}


//-------------------------------------------------
//  elapsed - return the amount of time since the
//  timer was started
//-------------------------------------------------

attotime emu_timer::elapsed() const
{
	return machine().time() - m_start;
}


//-------------------------------------------------
//  remaining - return the amount of time
//  remaining until the timer expires
//-------------------------------------------------

attotime emu_timer::remaining() const
{
	return m_expire - machine().time();
}


//-------------------------------------------------
//  register_save - register ourself with the save
//  state system
//-------------------------------------------------

void emu_timer::register_save()
{
	// determine our instance number and name
	int index = 0;
	astring name;

	// for non-device timers, it is an index based on the callback function name
	if (m_device == NULL)
	{
		name = m_callback.name();
		for (emu_timer *curtimer = machine().scheduler().first_timer(); curtimer != NULL; curtimer = curtimer->next())
			if (!curtimer->m_temporary && curtimer->m_device == NULL && strcmp(curtimer->m_callback.name(), m_callback.name()) == 0)
				index++;
	}

	// for device timers, it is an index based on the device and timer ID
	else
	{
		name.printf("%s/%d", m_device->tag(), m_id);
		for (emu_timer *curtimer = machine().scheduler().first_timer(); curtimer != NULL; curtimer = curtimer->next())
			if (!curtimer->m_temporary && curtimer->m_device != NULL && curtimer->m_device == m_device && curtimer->m_id == m_id)
				index++;
	}

	// save the bits
	machine().save().save_item("timer", name, index, NAME(m_param));
	machine().save().save_item("timer", name, index, NAME(m_enabled));
	machine().save().save_item("timer", name, index, NAME(m_period));
	machine().save().save_item("timer", name, index, NAME(m_start));
	machine().save().save_item("timer", name, index, NAME(m_expire));
}


//-------------------------------------------------
//  schedule_next_period - schedule the next
//  period
//-------------------------------------------------

void emu_timer::schedule_next_period()
{
	// advance by one period
	m_start = m_expire;
	m_expire += m_period;

	// remove and re-insert us
	device_scheduler &scheduler = machine().scheduler();
	scheduler.timer_list_remove(*this);
	scheduler.timer_list_insert(*this);
}


//-------------------------------------------------
//  dump - dump internal state to a single output
//  line in the error log
//-------------------------------------------------

void emu_timer::dump() const
{
	logerror("%p: en=%d temp=%d exp=%15s start=%15s per=%15s param=%d ptr=%p", this, m_enabled, m_temporary, m_expire.as_string(), m_start.as_string(), m_period.as_string(), m_param, m_ptr);
	if (m_device == NULL)
		logerror(" cb=%s\n", m_callback.name());
	else
		logerror(" dev=%s id=%d\n", m_device->tag(), m_id);
}



//**************************************************************************
//  DEVICE SCHEDULER
//**************************************************************************

//-------------------------------------------------
//  device_scheduler - constructor
//-------------------------------------------------

device_scheduler::device_scheduler(running_machine &machine) :
	m_machine(machine),
	m_executing_device(NULL),
	m_execute_list(NULL),
	m_basetime(attotime::zero),
	m_cothread(co_active()),
	m_timer_list(NULL),
	m_timer_allocator(machine.respool()),
	m_callback_timer(NULL),
	m_callback_timer_modified(false),
	m_callback_timer_expire_time(attotime::zero),
	m_quantum_list(machine.respool()),
	m_quantum_allocator(machine.respool()),
	m_quantum_minimum(ATTOSECONDS_IN_NSEC(1) / 1000)
{
	// append a single never-expiring timer so there is always one in the list
	m_timer_list = &m_timer_allocator.alloc()->init(machine, timer_expired_delegate(), NULL, true);
	m_timer_list->adjust(attotime::never);

	// register global states
	machine.save().save_item(NAME(m_basetime));
	machine.save().register_presave(save_prepost_delegate(FUNC(device_scheduler::presave), this));
	machine.save().register_postload(save_prepost_delegate(FUNC(device_scheduler::postload), this));
}


//-------------------------------------------------
//  device_scheduler - destructor
//-------------------------------------------------

device_scheduler::~device_scheduler()
{
	// remove all timers
	while (m_timer_list != NULL)
		m_timer_allocator.reclaim(m_timer_list->release());
}


//-------------------------------------------------
//  time - return the current time
//-------------------------------------------------

attotime device_scheduler::time() const
{
	// if we're currently in a callback, use the timer's expiration time as a base
	if (m_callback_timer != NULL)
		return m_callback_timer_expire_time;

	// if we're executing as a particular CPU, use its local time as a base
	// otherwise, return the global base time
	return (m_executing_device != NULL) ? m_executing_device->local_time() : m_basetime;
}


//-------------------------------------------------
//  can_save - return true if it's safe to save
//  (i.e., no temporary timers outstanding)
//-------------------------------------------------

bool device_scheduler::can_save() const
{
	// if any live temporary timers exit, fail
	for (emu_timer *timer = m_timer_list; timer != NULL; timer = timer->next())
		if (timer->m_temporary && timer->expire() != attotime::never)
		{
			logerror("Failed save state attempt due to anonymous timers:\n");
			dump_timers();
			return false;
		}

	// otherwise, we're good
	return true;
}


//-------------------------------------------------
//  timeslice - execute all devices for a single
//  timeslice
//-------------------------------------------------

void device_scheduler::timeslice()
{
	bool call_debugger = ((machine().debug_flags & DEBUG_FLAG_ENABLED) != 0);

	// build the execution list if we don't have one yet
	if (m_execute_list == NULL)
		rebuild_execute_list();

	// execute timers
	execute_timers();

	// loop until we hit the next timer
	while (m_basetime < m_timer_list->m_expire)
	{
		// by default, assume our target is the end of the next quantum
		attotime target = m_basetime + attotime(0, m_quantum_list.first()->m_actual);

		// however, if the next timer is going to fire before then, override
		if (m_timer_list->m_expire < target)
			target = m_timer_list->m_expire;

		LOG(("------------------\n"));
		LOG(("cpu_timeslice: target = %s\n", target.as_string()));

		// apply pending suspension changes
		UINT32 suspendchanged = 0;
		for (device_execute_interface *exec = m_execute_list; exec != NULL; exec = exec->m_nextexec)
		{
			suspendchanged |= exec->m_suspend ^ exec->m_nextsuspend;
			exec->m_suspend = exec->m_nextsuspend;
			exec->m_nextsuspend &= ~SUSPEND_REASON_TIMESLICE;
			exec->m_eatcycles = exec->m_nexteatcycles;
		}

		// recompute the execute list if any CPUs changed their suspension state
		if (suspendchanged != 0)
			rebuild_execute_list();

		// loop over non-suspended CPUs
		for (device_execute_interface *exec = m_execute_list; exec != NULL; exec = exec->m_nextexec)
		{
			// only process if our target is later than the CPU's current time (coarse check)
			if (target.seconds >= exec->m_localtime.seconds)
			{
				// compute how many attoseconds to execute this CPU
				attoseconds_t delta = target.attoseconds - exec->m_localtime.attoseconds;
				if (delta < 0 && target.seconds > exec->m_localtime.seconds)
					delta += ATTOSECONDS_PER_SECOND;
				assert(delta == (target - exec->m_localtime).as_attoseconds());

				// if we have enough for at least 1 cycle, do the math
				if (delta >= exec->m_attoseconds_per_cycle)
				{
					// compute how many cycles we want to execute
					int ran = exec->m_cycles_running = divu_64x32((UINT64)delta >> exec->m_divshift, exec->m_divisor);
					LOG(("  cpu '%s': %d cycles\n", exec->device().tag(), exec->m_cycles_running));

					// if we're not suspended, actually execute
					if (exec->m_suspend == 0)
					{
						g_profiler.start(exec->m_profiler);

						// note that this global variable cycles_stolen can be modified
						// via the call to cpu_execute
						exec->m_cycles_stolen = 0;
						m_executing_device = exec;
						*exec->m_icountptr = exec->m_cycles_running;
						if (!call_debugger)
							exec->run();
						else
						{
							debugger_start_cpu_hook(&exec->device(), target);
							exec->run();
							debugger_stop_cpu_hook(&exec->device());
						}

						// adjust for any cycles we took back
						assert(ran >= *exec->m_icountptr);
						ran -= *exec->m_icountptr;
						assert(ran >= exec->m_cycles_stolen);
						ran -= exec->m_cycles_stolen;
						g_profiler.stop();
					}

					// account for these cycles
					exec->m_totalcycles += ran;

					// update the local time for this CPU
					exec->m_localtime += attotime(0, exec->m_attoseconds_per_cycle * ran);
					LOG(("         %d ran, %d total, time = %s\n", ran, (INT32)exec->m_totalcycles, exec->m_localtime.as_string()));

					// if the new local CPU time is less than our target, move the target up, but not before the base
					if (exec->m_localtime < target)
					{
						assert(exec->m_localtime < target);
						target = max(exec->m_localtime, m_basetime);
						LOG(("         (new target)\n"));
					}
				}
			}
		}
		m_executing_device = NULL;

		// update the base time
		m_basetime = target;
	}
}


//-------------------------------------------------
//  abort_timeslice - abort execution for the
//  current timeslice
//-------------------------------------------------

void device_scheduler::abort_timeslice()
{
	if (m_executing_device != NULL)
		m_executing_device->abort_timeslice();
}


//-------------------------------------------------
//  trigger - generate a global trigger
//-------------------------------------------------

void device_scheduler::trigger(int trigid, attotime after)
{
	// ensure we have a list of executing devices
	if (m_execute_list == NULL)
		rebuild_execute_list();

	// if we have a non-zero time, schedule a timer
	if (after != attotime::zero)
		timer_set(after, timer_expired_delegate(FUNC(device_scheduler::timed_trigger), this), trigid);

	// send the trigger to everyone who cares
	else
		for (device_execute_interface *exec = m_execute_list; exec != NULL; exec = exec->m_nextexec)
			exec->trigger(trigid);
}


//-------------------------------------------------
//  boost_interleave - temporarily boosts the
//  interleave factor
//-------------------------------------------------

void device_scheduler::boost_interleave(attotime timeslice_time, attotime boost_duration)
{
	// ignore timeslices > 1 second
	if (timeslice_time.seconds > 0)
		return;
	add_scheduling_quantum(timeslice_time, boost_duration);
}


//-------------------------------------------------
//  timer_alloc - allocate a global non-device
//  timer and return a pointer
//-------------------------------------------------

emu_timer *device_scheduler::timer_alloc(timer_expired_delegate callback, void *ptr)
{
	return &m_timer_allocator.alloc()->init(machine(), callback, ptr, false);
}


//-------------------------------------------------
//  timer_set - allocate an anonymous non-device
//  timer and set it to go off after the given
//  amount of time
//-------------------------------------------------

void device_scheduler::timer_set(attotime duration, timer_expired_delegate callback, int param, void *ptr)
{
	m_timer_allocator.alloc()->init(machine(), callback, ptr, true).adjust(duration, param);
}


//-------------------------------------------------
//  timer_pulse - allocate an anonymous non-device
//  timer and set it to go off at the given
//  frequency
//-------------------------------------------------

void device_scheduler::timer_pulse(attotime period, timer_expired_delegate callback, int param, void *ptr)
{
	m_timer_allocator.alloc()->init(machine(), callback, ptr, false).adjust(period, param, period);
}


//-------------------------------------------------
//  timer_alloc - allocate a global device timer
//  and return a pointer
//-------------------------------------------------

emu_timer *device_scheduler::timer_alloc(device_t &device, device_timer_id id, void *ptr)
{
	return &m_timer_allocator.alloc()->init(device, id, ptr, false);
}


//-------------------------------------------------
//  timer_set - allocate an anonymous device timer
//  and set it to go off after the given amount of
//  time
//-------------------------------------------------

void device_scheduler::timer_set(attotime duration, device_t &device, device_timer_id id, int param, void *ptr)
{
	m_timer_allocator.alloc()->init(device, id, ptr, true).adjust(duration, param);
}


//-------------------------------------------------
//  eat_all_cycles - eat a ton of cycles on all
//  CPUs to force a quick exit
//-------------------------------------------------

void device_scheduler::eat_all_cycles()
{
	for (device_execute_interface *exec = m_execute_list; exec != NULL; exec = exec->m_nextexec)
		exec->eat_cycles(1000000000);
}


//-------------------------------------------------
//  timed_trigger - generate a trigger after a
//  given amount of time
//-------------------------------------------------

void device_scheduler::timed_trigger(void *ptr, INT32 param)
{
	trigger(param);
}


//-------------------------------------------------
//  presave - before creating a save state
//-------------------------------------------------

void device_scheduler::presave()
{
	// report the timer state after a log
	logerror("Prior to saving state:\n");
	dump_timers();
}


//-------------------------------------------------
//  postload - after loading a save state
//-------------------------------------------------

void device_scheduler::postload()
{
	// remove all timers and make a private list of permanent ones
	simple_list<emu_timer> private_list;
	while (m_timer_list != NULL)
	{
		emu_timer &timer = *m_timer_list;

		// temporary timers go away entirely (except our special never-expiring one)
		if (timer.m_temporary && timer.expire() != attotime::never)
			m_timer_allocator.reclaim(timer.release());

		// permanent ones get added to our private list
		else
			private_list.append(timer_list_remove(timer));
	}

	// now re-insert them; this effectively re-sorts them by time
	emu_timer *timer;
	while ((timer = private_list.detach_head()) != NULL)
		timer_list_insert(*timer);

	// report the timer state after a log
	logerror("After resetting/reordering timers:\n");
	dump_timers();
}


//-------------------------------------------------
//  compute_perfect_interleave - compute the
//  "perfect" interleave interval
//-------------------------------------------------

void device_scheduler::compute_perfect_interleave()
{
	// ensure we have a list of executing devices
	if (m_execute_list == NULL)
		rebuild_execute_list();

	// start with the first one
	device_execute_interface *first = m_execute_list;
	if (first != NULL)
	{
		// start with a huge time factor and find the 2nd smallest cycle time
		attoseconds_t smallest = first->minimum_quantum();
		attoseconds_t perfect = ATTOSECONDS_PER_SECOND - 1;
		for (device_execute_interface *exec = first->m_nextexec; exec != NULL; exec = exec->m_nextexec)
		{
			// find the 2nd smallest cycle interval
			attoseconds_t curquantum = exec->minimum_quantum();
			if (curquantum < smallest)
			{
				perfect = smallest;
				smallest = curquantum;
			}
			else if (curquantum < perfect)
				perfect = curquantum;
		}

		// if this is a new minimum quantum, apply it
		if (m_quantum_minimum != perfect)
		{
			// adjust all the actuals; this doesn't affect the current
			m_quantum_minimum = perfect;
			for (quantum_slot *quant = m_quantum_list.first(); quant != NULL; quant = quant->next())
				quant->m_actual = MAX(quant->m_requested, m_quantum_minimum);
		}
	}
}


//-------------------------------------------------
//  rebuild_execute_list - rebuild the list of
//  executing CPUs, moving suspended CPUs to the
//  end
//-------------------------------------------------

void device_scheduler::rebuild_execute_list()
{
	// if we haven't yet set a scheduling quantum, do it now
	if (m_quantum_list.first() == NULL)
	{
		// set the core scheduling quantum
		attotime min_quantum = machine().config().m_minimum_quantum;

		// if none specified default to 60Hz
		if (min_quantum == attotime::zero)
			min_quantum = attotime::from_hz(60);

		// if the configuration specifies a device to make perfect, pick that as the minimum
		if (machine().config().m_perfect_cpu_quantum != NULL)
		{
			device_t *device = machine().device(machine().config().m_perfect_cpu_quantum);
			if (device == NULL)
				fatalerror("Device '%s' specified for perfect interleave is not present!", machine().config().m_perfect_cpu_quantum);

			device_execute_interface *exec;
			if (!device->interface(exec))
				fatalerror("Device '%s' specified for perfect interleave is not an executing device!", machine().config().m_perfect_cpu_quantum);

			min_quantum = min(attotime(0, exec->minimum_quantum()), min_quantum);
		}

		// make sure it's no higher than 60Hz
		min_quantum = min(min_quantum, attotime::from_hz(60));

		// inform the timer system of our decision
		add_scheduling_quantum(min_quantum, attotime::never);
	}

	// start with an empty list
	device_execute_interface **active_tailptr = &m_execute_list;
	*active_tailptr = NULL;

	// also make an empty list of suspended devices
	device_execute_interface *suspend_list = NULL;
	device_execute_interface **suspend_tailptr = &suspend_list;

	// iterate over all devices
	device_execute_interface *exec = NULL;
	for (bool gotone = machine().devicelist().first(exec); gotone; gotone = exec->next(exec))
	{
		// append to the appropriate list
		exec->m_nextexec = NULL;
		if (exec->m_suspend == 0)
		{
			*active_tailptr = exec;
			active_tailptr = &exec->m_nextexec;
		}
		else
		{
			*suspend_tailptr = exec;
			suspend_tailptr = &exec->m_nextexec;
		}
	}

	// append the suspend list to the end of the active list
	*active_tailptr = suspend_list;
}


//-------------------------------------------------
//  timer_list_insert - insert a new timer into
//  the list at the appropriate location
//-------------------------------------------------

emu_timer &device_scheduler::timer_list_insert(emu_timer &timer)
{
	// disabled timers sort to the end
	attotime expire = timer.m_enabled ? timer.m_expire : attotime::never;

	// loop over the timer list
	emu_timer *prevtimer = NULL;
	for (emu_timer *curtimer = m_timer_list; curtimer != NULL; prevtimer = curtimer, curtimer = curtimer->next())
	{
		// if the current list entry expires after us, we should be inserted before it
		if (curtimer->m_expire > expire)
		{
			// link the new guy in before the current list entry
			timer.m_prev = curtimer->m_prev;
			timer.m_next = curtimer;

			if (curtimer->m_prev != NULL)
				curtimer->m_prev->m_next = &timer;
			else
				m_timer_list = &timer;

			curtimer->m_prev = &timer;
			return timer;
		}
	}

	// need to insert after the last one
	if (prevtimer != NULL)
		prevtimer->m_next = &timer;
	else
		m_timer_list = &timer;

	timer.m_prev = prevtimer;
	timer.m_next = NULL;
	return timer;
}


//-------------------------------------------------
//  timer_list_remove - remove a timer from the
//  linked list
//-------------------------------------------------

emu_timer &device_scheduler::timer_list_remove(emu_timer &timer)
{
	// remove it from the list
	if (timer.m_prev != NULL)
		timer.m_prev->m_next = timer.m_next;
	else
		m_timer_list = timer.m_next;

	if (timer.m_next != NULL)
		timer.m_next->m_prev = timer.m_prev;

	return timer;
}


//-------------------------------------------------
//  execute_timers - execute timers and update
//  scheduling quanta
//-------------------------------------------------

void device_scheduler::execute_timers()
{
	// if the current quantum has expired, find a new one
	while (m_basetime >= m_quantum_list.first()->m_expire)
		m_quantum_allocator.reclaim(m_quantum_list.detach_head());

	LOG(("timer_set_global_time: new=%s head->expire=%s\n", m_basetime.as_string(), m_timer_list->m_expire.as_string()));

	// now process any timers that are overdue
	while (m_timer_list->m_expire <= m_basetime)
	{
		// if this is a one-shot timer, disable it now
		emu_timer &timer = *m_timer_list;
		bool was_enabled = timer.m_enabled;
		if (timer.m_period == attotime::zero || timer.m_period == attotime::never)
			timer.m_enabled = false;

		// set the global state of which callback we're in
		m_callback_timer_modified = false;
		m_callback_timer = &timer;
		m_callback_timer_expire_time = timer.m_expire;

		// call the callback
		if (was_enabled)
		{
			g_profiler.start(PROFILER_TIMER_CALLBACK);

			if (timer.m_device != NULL)
				timer.m_device->timer_expired(timer, timer.m_id, timer.m_param, timer.m_ptr);
			else if (!timer.m_callback.isnull())
				timer.m_callback(timer.m_ptr, timer.m_param);

			g_profiler.stop();
		}

		// clear the callback timer global
		m_callback_timer = NULL;

		// reset or remove the timer, but only if it wasn't modified during the callback
		if (!m_callback_timer_modified)
		{
			// if the timer is temporary, remove it now
			if (timer.m_temporary)
				m_timer_allocator.reclaim(timer.release());

			// otherwise, reschedule it
			else
				timer.schedule_next_period();
		}
	}
}


//-------------------------------------------------
//  add_scheduling_quantum - add a scheduling
//  quantum; the smallest active one is the one
//  that is in use
//-------------------------------------------------

void device_scheduler::add_scheduling_quantum(attotime quantum, attotime duration)
{
	assert(quantum.seconds == 0);

	attotime curtime = time();
	attotime expire = curtime + duration;

	// figure out where to insert ourselves, expiring any quanta that are out-of-date
	quantum_slot *insert_after = NULL;
	quantum_slot *next;
	for (quantum_slot *quant = m_quantum_list.first(); quant != NULL; quant = next)
	{
		// if this quantum is expired, nuke it
		next = quant->next();
		if (curtime >= quant->m_expire)
			m_quantum_allocator.reclaim(m_quantum_list.detach(*quant));

		// if this quantum is shorter than us, we need to be inserted afterwards
		else if (quant->m_requested <= quantum.attoseconds)
			insert_after = quant;
	}

	// if we found an exact match, just take the maximum expiry time
	if (insert_after != NULL && insert_after->m_requested == quantum.attoseconds)
		insert_after->m_expire = max(insert_after->m_expire, expire);

	// otherwise, allocate a new quantum and insert it after the one we picked
	else
	{
		quantum_slot &quant = *m_quantum_allocator.alloc();
		quant.m_requested = quantum.attoseconds;
		quant.m_actual = MAX(quantum.attoseconds, m_quantum_minimum);
		quant.m_expire = expire;
		m_quantum_list.insert_after(quant, insert_after);
	}
}


//-------------------------------------------------
//  dump_timers - dump the current timer state
//-------------------------------------------------

void device_scheduler::dump_timers() const
{
	logerror("=============================================\n");
	logerror("Timer Dump: Time = %15s\n", time().as_string());
	for (emu_timer *timer = first_timer(); timer != NULL; timer = timer->next())
		timer->dump();
	logerror("=============================================\n");
}


